Nassar pleaded guilty in July to three charges of obtaining and possessing child pornography and destroying computer files to hamper an investigation. Investigators found more than 37,000 images of child pornography on hard drives at Nassar's home while investigating sexual assault claims made against him.

"You have to wonder whether he felt he was omnipotent, whether he felt he was getting away with something so cleverly," said U.S. District Judge Janet Neff.

Nassar was sentenced to 20 years on each of three counts, to be served consecutively.

He will receive additional prison time in January, when he is sentenced on 10 sexual assault charges. Nassar pleaded guilty to all 10 charges in November.